Saturday, August 04, 2012

James Hansen has an op-ed in the Washington Post, which might be thought of as a reply to Richard Muller, but is more an example of Alley's folks, you have the blue one over here, and the green one over there, but what you are not listening to are the people who study and really know about this stuff over there in the corner yelling bloody murder.

By James E. Hansen, Published: August 3

James E. Hansen directs the NASA Goddard Institute for Space Studies.

When I testified before the Senate in the
hot summer of 1988
, I warned of the kind of future that climate change would bring
to us and our planet. I painted a grim picture of the consequences of
steadily increasing temperatures, driven by mankind’s use of fossil
fuels.

69 comments:

Anonymous
said...

"Renewable electricity generation from technologies that are commercially available today, in combination with a more flexible electric system, is more than adequate to supply 80% of total U.S. electricity generation in 2050 while meeting electricity demand on an hourly basis in every region of the country."

I have to say the best of the commentators over there has to be "WingnutTrollInstructor":

"I must be ending my observation duties of the students we've educated into wingnut climate trolling. I do hope everyone understands that we don't have the best of students and you can probably understand why. No intelligent person could stomach being a wingnut, much less a wingnut climate troll, so the group of people we must choose from has a severely low intelligence upper bound. Then, of course, we can't just allow any body to be a wingnut climate troll, so there must be an intelligence lower bound.

Unfortunately, it's clear our graduates were not screened well enough and the intelligence lower bound was not honored. We are working hard on our admissions process to avoid this in the future. Please be patient. We are working hard on it.

"Message for James Inhofe! It’s so hot in Oklahoma that this squirrel melted"

It's pretty sad, really. One aspect of all this that I don't understand is how much we ignore the impact on other species. They don't have aircon, or any other means to manage the change than to move to cooler areas. In this modern day, with so much human presence, that can be difficult. There is also no grand co-ordinator of species to ensure they all move together at the same time, or that there aren't physical barriers in the way.

Temperatures like those can be the limit for many species. Birds literally fall out of trees, as do bats. These extreme events don't add much to the yearly average, but they can be devestating to many species.

One reason he got the attention he did in 1988 was there was a big drought that year in the mid west.

He wasn't the only voice speaking out back then saying global warming was causing changes that were already evident - maybe it was the fact he said he was 99% certain about it. It was the first time many ordinary people heard about the issue.

I'm glad Hansen is still with us speaking out. The drought is going to have to get far worse to break up whatever has so many minds seized up in denial though.

Eg: Anne Duignan, New York based analyst for JPMorgan Chase & Co., was interviewed by Tom Keene for Bloomberg Radio, aired on Bloomberg Surveillance, July 10, 2012. The topic was the drought and its effect on corn production. (The US corn industry is a $75 billion dollar annual activity).

Tom Keene: “Is there a sense here of global warming, or is the sense this is a cyclical tough time?”Anne Duignan: “I would say that most people in the agricultural industry assume that this is cyclical, since we have precedent. We’ve had huge cycles in weather through the ages. So I don’t think anybody is calling this global warming at this point.”

This is demonstrably false. Even Skeptical Science (a site that firmly believes in anthropogenic global warming) recognizes Hansen’s projections have failed the test of time:http://www.skepticalscience.com/Hansen-1988-prediction.htm

To refresh memories: Scenario A assumed an exponential growth in greenhouse gas forcings (GHGs).Scenario B assumed a linear increase in GHGs.Scenario C assumed a constant GHG forcing after year 2000 (no more increase in GHGs after 2000).

Hansen explained that humanity needed follow Scenario C (stop emitting GHGs after year 2000) to stabilize temperatures and save the planet. Since Hansen’s presentation, atmospheric carbon dioxide concentrations have continued to increase between Scenario A and Scenario B, yet somehow temperature has trended right along with Scenario C. Mythbuster’s would declare Hansen’s projections: “BUSTED”.

Hansen also says “the Russian heat wave of 2010 is not simply an example of what climate change could bring. It is caused by climate change.”

I often think that things are potentially worse than people realise. Not slow climate change but the potential for abrupt and non linear change. Changes in temperature of 10's of degrees in places in as little as a decade. A report was published in 2002 by the US National Academy of Sciences - Abrupt climate change: inevitable surprises - that describes this as the new climate paradigm. But it is a paradigm that is making slow progress despite support in scientific literature, the Woods Hole Oceanographic Institute, the Royal Society...

So where might some of these surprises come from? To quote AR4 section 3.4.4.1. 'In summary, although there is independent evidence for decadal changes in TOA radiative fluxes over the last two decades, the evidence is equivocal. Changes in the planetary and tropical TOA radiative fluxes are consistent with independent global ocean heat-storage data, and are expected to be dominated by changes in cloud radiative forcing. To the extent that they are real, they may simply reflect natural low-frequency variability of the climate system.' The earlier satellite data is most reliably ERBS and ISCCP-FD. It shows cooling in the infrared and warming in the short wave – that (if real) must arise as a result of change in cloud cover...

It is a pretty good fit. But it is all just data and as good as the instruments and modelling.

We also have CERES – clouds and Earth’s radiant energy system – measuring Earth’s radiant energy out in reflected sw and emitted lw with unprecedented accuracy. It shows that there is some missing energy that should be there in the Earth system when considering the lack of tropospheric warming last decade. Again the big change is in SW. The interannual changes are largely related to ENSO and might provide one clue as to a source of ‘low frequency variability of the climate system.’

...More recent work is identifying abrupt climate changes working through the El Niño Southern Oscillation, the Pacific Decadal Oscillation, the North Atlantic Oscillation, the Southern Annular Mode, the Artic Oscillation, the Indian Ocean Dipole and other measures of ocean and atmospheric states. These are measurements of sea surface temperature and atmospheric pressure over more than 100 years which show evidence for abrupt change to new climate conditions that persist for up to a few decades before shifting again. Global rainfall and flood records likewise show evidence for abrupt shifts and regimes that persist for decades. In Australia, less frequent flooding from early last century to the mid 1940’s, more frequent flooding to the late 1970’s and again a low rainfall regime to recent times.

Anastasios Tsonis, of the Atmospheric Sciences Group at University of Wisconsin, Milwaukee, and colleagues used a mathematical network approach to analyse abrupt climate change on decadal timescales. Ocean and atmospheric indices – in this case the El Niño Southern Oscillation, the Pacific Decadal Oscillation, the North Atlantic Oscillation and the North Pacific Oscillation - can be thought of as chaotic oscillators that capture the major modes of climate variability. Tsonis and colleagues calculated the ‘distance’ between the indices. It was found that they would synchronise at certain times and then shift into a new state.

It is no coincidence that shifts in ocean and atmospheric indices occur at the same time as changes in the trajectory of global surface temperature. Our ‘interest is to understand - first the natural variability of climate - and then take it from there. So we were very excited when we realized a lot of changes in the past century from warmer to cooler and then back to warmer were all natural,’ Tsonis said.

‘This paper provides an update to an earlier work that showed specific changesin the aggregate time evolution of major Northern Hemispheric atmospheric and oceanic modes of variability serve as a harbinger of climate shifts. Specifically, when the major modes of Northern Hemisphere climate variability are synchronized, or resonate, and the coupling between those modes simulta neously increases, the climate system appears to be thrown into a new state, marked by a break in the global mean temperature trend and in the character of El Nin˜o/Southern Oscillation variability.’ (Swanson et al 2009 – Has the climate recently shifted)

‘While in the observations such breaks in temperature trend are clearly superimposed upon a century time-scale warming presumably due to anthropogenic forcing, those breaks result in significant departures from that warming over time periods spanning multiple decades. Using a new measure of coupling strength, this update shows that these climate modes have recently synchronized, with synchronization peaking in the year 2001/02. This synchronization has been followed by an increase in coupling. This suggests that the climate system may well have shifted again, with a consequent break in the global mean temperature trend from the post 1976/77 warming to a new period (indeterminate length) of roughly constant global mean temperature.’ (Op. cit.)

‘Make everything as simple as possible, but not simpler. Albert Einstein

"Temperatures like those can be the limit for many species. Birds literally fall out of trees, as do bats. These extreme events don't add much to the yearly average, but they can be devestating to many species."

This is so much more important than most readers probably appreciate at first blush.

It's the alteration of the pattern of extreme events that affects species, fauna/flora communities, and whole ecosystems. Whilst there is a lot of resilience in natural systems, the changes that humans have wrought - and are continuing to wring - on the planet push many species and associations beyond their ecophysiological tolerances.

It's for this reason that much of our biodiversity is doomed to extinction, and why much of our food productivity is looking down the barrel of a cannon.

In the Hansen wasn't the only one back in 1988 who was speaking out saying climate change is already evident department - here's what some other scientists signed at the Toronto Changing Atmosphere conference, held a few days after Hansen's 1988 testimony. "Humanity is conducting an... experiment whose ultimate consequences could be second only to a global nuclear war", "these changes represent a major threat to international security and are already having harmful consequences over many parts of the globe", etc., et supposedly delusionally cetera. The full statement is here http://www.cmos.ca/ChangingAtmosphere1988e.pdf

For the Muller on Hansen department:

There is this Muller lecture. http://www.youtube.com/watch?v=8BQpciw8suk

Muller struts back and forth in front of a projection of the Mann et.al. hockey stick chart in high dudgeon. He denounces it, Mann et.al, and climate science in general. He then announces he's going to come up enough with his BEST (worst?) study that Hansen will have to take notice:

“Jim Hansen who predicts things ahead of time, he’s going to find we have a group here [Mann et.al.] who feels it is legitimate to hide things. This is why I’m now leading a study to redo all this in a totally transparent way”

According to Muller, the original Mann et.al. paper, "would not have survived peer review in any journal I'm willing to publish in".

I guess that rules out Nature (publishers of MBH98) and presumably GRL (publishers of MBH99) as completely tainted ("you are not allowed to do this in science") and therefore unsuitable as hosts for the BEST (sic) (sick?) paper.

I wonder if any journal Mann ever published in would now be unsuitable for Muller.

Louis Hooffstetter said about Hansen’s statement: “My projections about increasing global temperature (in 1988 Senate testimony) have been proved true.” This is demonstrably false. Even Skeptical Science (a site that firmly believes in anthropogenic global warming) recognizes Hansen’s projections have failed the test of time: http://www.skepticalscience.com/Hansen-1988-prediction.htm

J Bowers said “Your conclusion about the SkS article is demonstrably false”, and cited a number of articles that attempt to show green house gas (GHG) emissions fall close to Hansen’s Scenario B.

The conclusion that since 1988, the worldwide GHG emission scenario falls somewhere between Hansen’s Scenario A and Scenario B is based on a well known graph: http://www-das.uwyo.edu/~geerts/cwx/notes/chap01/mauna_loa_co2.gif

This is irrefutable empirical data. It’s clear that since 1988, carbon dioxide emissions alone have increased somewhere between a logrithmic trend (Scenario A) and a linear trend (Scenario B). Additionally this graph doesn’t take into account atmospheric increases of any of the other 17 GHGs listed in the IPCC’s Third Assessment Report; nor does it take into account atmospheric increases in water vapor, (which is not listed in the TAR as a GHG). Authors / bloggers who try to convince the bunnies that GHG emissions have only increased in accordance with Scenario B, are liars. They want Hansen’s projection to approximate Scenario B so its’ failure to predict reality appears less dismal.

As for Kevin Trenberth’s statement (concerning Hansen’s NOAA colleagues who disagree with him): “Many statements are not justified and are actually irresponsible”, Trenberth should certainly know. He’s made many irresponsible and unjustified statements concerning anthropogenic global warming himself: http://www.scientificamerican.com/article.cfm?id=warmer-oceans-stronger-hurricanes. Since his pronouncement in July of 2007 that warmer oceans lead to more frequent and more powerful hurricanes, absolutely ZERO hurricanes have made landfall in the US. The last one to come close (Hurricane Irene in August of 2011) petered out just shy of the Outer Banks of NC. Despite what Wikipedia says, none of the near shore sea buoys nor land based anemometers recorded sustained hurricane force winds.

CO2 emissions may have been between A and B, but total forcings from all emissions have been between B and C.

I don't know why you try to counter an argument about increasing hurricane strength with whether or not hurricanes have made landfall in the US. It really doesn't make sense as an argument. And the research I'm aware of points to a decrease in hurricane frequency but an increase in category 3s and above.

Although Hansen's projected global temperature [1988] increase has been higher than the actual global warming, this is because his climate model used a high climate sensitivity parameter. Had he used the currently accepted value of approximately 3°C warming for a doubling of atmospheric CO2, Hansen would have correctly projected the ensuing global warming

Or this?

Hansen et al. (1981) demonstrates that we have every reason to be concerned, as three decades ago these climate scientists understood the workings of the global climate well enough to predict the ensuing global warming within approximately 15%, and accurately predict a number of important consequences. It's high time that we start listening to these climate experts and reduce our greenhouse gas emissions.

It's pretty simple, the Hansen et al., 1988 emission scenario B was right on the money as shown in detail by skeptical science (Eli did a series on these when Roger the Jr. was throwing lxixexsx extremely misleading statements that only are anything but lies under a set of improbable assumptions but which will be defended bitterly and unendingly very similar to Louis').------------------------"Total Scenario B greenhouse gas radiative forcing from 1984 to 2010 = 1.1 W/m2

The actual greenhouse gas forcing from 1984 to 2010 was approximately 1.06 W/m2 (NASA GISS). Thus the greenhouse gas radiative forcing in Scenario B was too high by about 5%."--------------------

the problem was that the climate sensitivity was too high, but that only had an effect recently after over 20 years. As Hansen said

For anyone interested in what Hansen actually said (rather than simply what some who obviously never read his paper think he said), Deltoid has some of the most important extracts

Hansen's projections A and C were intended to "bracket" future emissions with scenario B considered by Hansen as "perhaps the most plausible of the three cases".

Hansen certainly never claimed to be a soothsayer who could predict humanity's future emissions (and anyone who intimates as much has no clue what they are talking about)

Hansen also acknowledge the uncertainties in his model:

"Principal uncertainties in the predictions involve the equilibrium sensitivity of the model to climate forcing, the assumptions regarding heat uptake and transport by the ocean, and the omission of other less-certain climate forcings."

To refresh, Hansen said “My projections about increasing global temperature (in 1988 Senate testimony) have been proved true.” And I said that is demonstrably false. The graph in the Skeptical Science article shows Hansen’s projections compared to actual temperature data, and the article states “Hansen’s projected global temperature (1988) has been higher than the actual global warming…” The reasons why are irrelevant. You can adjust the forcings all you want (after the fact), but his 1998 Scenario A and Scenario B are busted. Look at the graph. You’re delusional if you continue to believe his 1998 model projections approximate anything close to reality.

Skeptical Science admits that since making his 1988 projections, Hansen has been forced to lower the climate sensitivity of his models to make them approximate reality. But then they say “three decades ago these climate scientists understood the workings of the global climate well enough to predict the ensuing global warming…, and accurately predict a number of important consequences.” What a blatant contradiction! Obviously three decades ago `climatologists didn’t understand the workings of the global climate well enough to predict the ensuing global warming. If they did, they wouldn’t have been forced to lower the climate sensitivity of their models to make them approximate reality.

Speaking of “accurately predicting… important consequences (of AGW)” please provide a list of weather events that climatologists don’t predict as “important consequences of AGW”. EVERYHTING is attributed to atmospheric warming caused by man, even earthquakes deep in the crust, (which can’t possibly be true). It’s a sucker’s bet (if you believe it), because when you attribute every weather event to AGW, you’re can point to every storm, drought, tornado, hurricane, earthquake, yada, yada, yada and say “See! That’s just what I was talking about!” Sound familiar? The truth is, very little empirical data links weather events or trends to human attribution. Feel free to provide links to such data if possible.

Steve Bloom:

“When archaeologists discovered thousands of medieval skeletons in a mass burial pit in east London in the 1990s, they assumed they were 14th-century victims of the Black Death or the Great Famine of 1315-17. Now they have been astonished by a more explosive explanation – a cataclysmic volcano that had erupted a century earlier, thousands of miles away in the tropics, and wrought havoc on medieval Britons.”

“A century earlier, thousands of miles away in the tropics”? Really? Please explain how that works.

Does anyone know who, in 1988, made the closest projection of global surface temperature compared to actuals of the past twenty four years?

I will bet my bottom dollar that Hansen in 1988 was much closer to the mark than Louis Hooffstetter was in 1988.

Who gave the most accurate (in hindsight) estimate in regard to emissions, deforestation, aerosols, economic growth and dips, climate sensitivity - individually and together? Were there many people properly attempting to make projections back then? (Serious question - let's include economists because most of those estimates rely more on economics than climate science.)

Hansen, with a small number of others, was prepared to speak out and warn the world of what is happening, right from the word go.

I am sure the Louis Hooffstetters of the world will not be remembered as heroes by anyone at all in the future.

What Hooffstetter claimed Trenberth said "...his pronouncement in July of 2007 that warmer oceans lead to more frequent and more powerful hurricanes..."

What Trenberth actually said"Both observations and theory therefore suggest that hurricanes are becoming more intense as the earth warms. It is difﬁcult to say if the absolute number of cyclones is likely to increase, however, because tropical storms are much more effective than average thunderstorms at removing heat from the ocean. One big storm may also be more effective than two smaller ones, so it is possible or even likely that fewer cyclones might form ..."

Given the verballing of Trenberth, I assume this guy is a refugee from WUWT. Perhaps he could explain why he thinks warmer SSTs would result in weaker hurricanes. Perhaps he could even write a paper...

And given the effects we are seeing unfold--most lately in Oklahoma and with Arctic sea ise--I don't think Hansen is incorrect to feel he was somewhat of a Pollyana. Drought and melting Arctic ice are two areas where science has been well behind reality in terms of severity.

In fact, McIntyre has been known to do "statistics" on papers without even understanding what they were about -- or without "parsing" them as McIntyre describes his lack of due diligence on the latest Watts paper for which he did the stats.

I certainly don’t believe warmer SSTs result in weaker hurricanes - logically, they should make them stronger. And Trenberth is correct that tropical storms are much more effective than average thunderstorms at removing heat from the ocean. Despite this, the empirical data doesn’t support his 2007 claims:

http://policlimate.com/tropical/north_atlantic_hurricane.png

As for more frequent storms, in the 2007 Sci Am article Trenberth never specifically declares warmer oceans cause more hurricanes, but page 45 says “Even a small increase in the ocean’s warmth can turn more tropical disturbances into hurricanes…”, and page 48 features a chart titled “Storms On The rise” accompanied by ` the statement: “Since the mid 1990s the number of named tropical storms and hurricanes in the North Atlantic has been high”. To paraphrase Trenberth, the implication that warmer oceans produce more hurricanes is “robust”:

http://www.angelfire.com/folk/thegrieves/transfer/200707.pdf

Anonymous 5/8/12 3:00 PM:

See the first link. If you mean that a 15 year period (since 2007) is too short to make any conclusive determination about increasing hurricane strength versus hurricane landfalls, you are correct. That being said, as of today Trenberth’s 2007 hurricane projection isn’t withstanding the test of time. This makes his critique of Hansen’s NOAA colleagues: “Many statements are not justified and are actually irresponsible”, equivalent to ‘the pot calling the kettle black’. Trenberth’s credibility as a climatologist is tarnished by his inability to correctly project hurricane trends over the past 15 years.

Toby:

Regarding Skeptical Science’s statement: “Hansen’s projected global temperature (1988) has been higher than the actual global warming…” I said “The reasons why are irrelevant” because they are. You may not think so, but the acid test for a climate model is reality. A model that fails to simulate reality is wrong - period. The reasons why are irrelevant.

No thanks. Science doesn't give a whit about maturity or your cultural preconceptions, and I have better things to do than to try to educate ignoramuses. I've been doing this for a long time as well, probably longer than you've been alive.

So if you don't mind, of course, I'll just continue to be me.

It works for me. And it gets results. At least it gets the results that I'm after.

And in that end, that's all that counts - for me. I'm selfish that way.

And I pointed out that you were a vociferous supporter of the Wegman group's work, which has been extensively and carefully deconstructed and shown to be scientifically unsupportable, from its fawning over the incorrect claims about the statistics of the 'hockey stick', through to the large reliance on plagiarism that reflects an overall absence of anything resembling acceptable academic standards on the part of Wegman et al.

You have form when it comes to putting your money on notions that gallop off in the opposite direction to the truth. Perhaps you could address that previous grievous mishandling of matters scientific, in addition to properly responding to J Bower's post above, amongst others.

And if your game is to focus on style rather than substance, well, perhaps you should be wearing a millinery monstrosity and watching those jockies through binoculars with one eye tightly shut. There are horses for courses, and the cross-country briar patch is a little more prickly than the smooth staights of, say, Skeptical Science. If you don't like the way you're called out here, perhaps you should consider something more suited to your temperament; something like joining a knitting circle, or enrolling in a macrame class.

"Since his pronouncement in July of 2007 that warmer oceans lead to more frequent and more powerful hurricanes, absolutely ZERO hurricanes have made landfall in the US. The last one to come close (Hurricane Irene in August of 2011) petered out just shy of the Outer Banks of NC."

"Catastrophe modeling company Eqecat, whose software is used by insurers to predict exposure to disasters, estimated the economic losses in the United States from Hurricane Irene at more than $10 billion.

"Irene was the 10th weather-related disaster resulting in $1 billion or more in damage so far this year, the highest annual number of big disasters in 31 years, according to the NationalClimatic Data Center."

Louis, I'm gonna guess that you aren't a scientist. Some of the most interesting questions concern why and how models fail. Scientists learn by making models fail. I would suggest your attitude might explain your lack of understanding.

Hansen's statement that he was "too optimistic" refers to the recent events (eg occurrence of extreme temperatures (heat waves) in certain regions, accelerated melting of Greenland and arctic sea ice) that even Hansen did not expect back in '88 to see with relatively small increase in the global temperature.

And the climate sensitivity that Hansen was assuming for his model was very likely too large, which means that the temperature change has actually been smaller than he expected (

This is undoubtedly what frightens Hansen most of all (and what makes the criticisms of him like what we see above extremely ironic)

At least some aspects of the climate appear to be behaving non-linearly, with relatively large changes for small inputs.

As long as the arctic is warming faster than the mid latitudes we will continue to have weird weather. If global temps don't increase as fast as projected that just means we have a bit longer before most of the US and Europe become dust bowls. But even now I don't think it will make much difference for the SW, TX, OK, the middle east and Africa.

Martin Vermeer said...“A model that fails to simulate reality is wrong - period.”Louis, does your very demanding standard also apply to the Ostrich Model?

I’m not sure if the acid test for climate models applies to the Ostrich Model, but it certainly applies to climate models used to generate global temperature projections from IPCC AR4. Since these are the foundation of Vermeer & Rahmstorf 2009, let’s hope they withstand the test of time better than Hansen’s 1988 climate projections. If not, Vermeer & Rahmstorf 2009 is “Garbage-In, Garbage-Out”.

You are an idiot Louis as no model will ever 'simulate reality'. Whatever 'simulate reality' means

What you need to do is quantify how 'wrong' the model is. You need to set bounds on what is 'right' and what is 'wrong'. My guess is you don;t know how and would rather just wave your arms about claiming the models are wrong.

In his opening statement of his testimony to Congress in 1988, Dr Hansen spoke of three main conclusions:1. Number one the earth is warmer in 1988 than at any time in the history of instrumental records.2. Number two, global warming is now large enough that we can ascribe with a high degree of confidence a cause and effect relationship to the greenhouse effect.3. And, number three, our computer climate simulations indicate that the greenhouse effect is already large enough to begin to affect the probability of extreme events such as summer heat waves.

Hansen's latest paper supports point 3, presenting evidence of the past sixty years comparing two 30-year periods. (The first two points are accepted and well understood these days.)

One of my pet peeves is the (deliberate) conflation of wrong(inaccurate) with wrong(conceptually). All models are inaccurate, and simplified models trade off accuracy for speed. Denialist models that are based on the postulate from Gerlich & Teuschner that cooler CO2 aloft cannot radiate towards the earth because that would be a violation of the Second Law are wrong. (Another one is the difference between counting and measuring, but that's the subject of another rant).

The statement "A model that fails to simulate reality is wrong - period." reveals that Louis Hoofstetter does not understand fits, error bars, and statistics.

Anonymous @7/8/12 7:00 PM said "What you need to do is quantify how 'wrong' the model is."

Relative to what? Unless you live in an dream world, the only measuring stick climate models can be judged against is reality. What measuring stick would you propose we use to judge how 'wrong' a model is? The bottom line is that if a model fails to predict what actually happens, something is obviously 'wrong'.

How 'wrong' were hansen's 1998 projections? They missed the target, they missed the dart board, and they barely hit the wall. Without tweaking the forcings after the fact, they were almost 100% 'wrong'. And 'hindcasting' doesn't count. It's cheating. You can make a model hindcast almost whatever you want simply by adjusting the aerosol forcing from volcanoes.

How 'wrong' were hansen's 1998 projections? Without tweaking the forcings after the fact, they were almost 100% 'wrong'."

Actually, as Real climate says, "the Hansen et al ‘B’ projection is running warm compared to the real world (exactly how much warmer is unclear)."

But it's most probably NOT running "almost 100% warmer".

If one bases the estimate for temperature change on trends taken from the observational data and scenario B projection (which minimizes the impact of unforced variability on the result), the difference is more likely about 55-65% (depending on choice of temp data set for comparison), as one can see on this graph

Given the uncertainties in the trends, the difference could be more ...but then again could also be less.

At any rate, it's important to use trends (as opposed to just taking the difference between individual years)and to consider uncertainties in those trends when comparing observed temperature development to model results.

Hooffstetter cluelessly wrote: “A century earlier, thousands of miles away in the tropics”? Really? Please explain how that works."

Were you born yesterday? Explosive volcanoes located in the tropics will influence global climate because their aerosols can disperse into the stratosphere above both the northern and southern hemispheres. Think Pinatubo. Volcanoes located above 40 degrees latitude, on the other hand, can only influence the hemisphere in which they are located. (Super volcanoes like Yellowstone excepted.)

Or did you mean the "century earlier" part? That simply refers to the fact that the deaths occurred a century earlier than previously thought.

Hooffstetter also cluelessly wrote: "Since [Trenberth’s] pronouncement in July of 2007 that warmer oceans lead to more frequent and more powerful hurricanes, absolutely ZERO hurricanes have made landfall in the US."

Apparently Hooffstetter was born yesterday. It is known that while the annual global number of tropical cyclones has not increased, the number of powerful tropical cyclones has increased globally, and that consequently total accumulated cyclone energy has increased. The "made landfall in the US" gives away his game of "look a squirrel", never mind his ignorant mischaracterization of the impact of Hurricane Irene.

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Eli Rabett

Eli Rabett is a not quite failed professorial techno-bunny, a chair election from retirement, at a wanna be research university that has a lot to be proud of but has swallowed the Kool-Aid. The students are naive but great and the administrators vary day-to-day between homicidal and delusional. His colleagues are smart, but they have a curious inability to see the holes that they dig for themselves. Prof. Rabett is thankful that they occasionally heed his pointing out the implications of the various enthusiasms that rattle around the department and school. Ms. Rabett is thankful that Prof. Rabett occasionally heeds her pointing out that he is nuts.